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Abstract:

A lactic acid component (e.g., lactic acid or oligo (lactic acid)) can be
obtained by extraction from a lactic acid fermentation liquor with a pH
of 4.8 or less, using at least one solvent selected from the group
consisting of toluene, xylene, mesitylene, ethylbenzene, methanol,
ethanol, propanol, butanol, and mineral spirit. Furthermore, oligo
(lactic acid) can be obtained, by heating a lactic acid fermentation
liquor with a pH of 4.8 or less under reduced pressure, and washing, with
water, the fermentation liquor containing a produced oligo (lactic acid).
Hence, a method is provided for separating a lactic acid component from a
lactic acid fermentation liquor, which is free from incorporation of
impurities and which includes simple steps.

Claims:

1-12. (canceled)

13. A method for producing oligo (lactic acid) from a lactic acid
fermentation liquor, comprising the steps of:adding at least one solvent
selected from the group consisting of toluene, xylene, mesitylene,
ethylbenzene, and mineral spirit, to a lactic acid fermentation liquor
with a pH of 4.8 or less;heating the solvent added lactic acid
fermentation liquor with agitaion for azeotropy and then to a temperature
ranging from the azeotropic point of the solvent and water to 150.degree.
C., whereby the fermentation liquor is dehydrated and a lactic acid
component in the fermentation liquor is condensed to produce oligo
(lactic acid) with a weight-average molecular weight of not greater than
5000;heating the solvent added fermentation liquor which contains the
oligo (lactic acid) with agitaion to a temperature ranging from
60.degree. C. to 150.degree. C. to dissolve the oligo (lactic acid) in
the heated solvent for extraction;stopping the agitation while keeping
the heating to separate the solvent in which the oligo (lactic acid) is
dissolved from the fermentation liquor; andcooling down the separated
solvent to near room temperature to collect the oligo (lactic acid).

14. A method for producing oligo (lactic acid) from a lactic acid
fermentation liquor, comprising the steps of:heating a lactic acid
fermentation liquor with a pH of 4.8 or less to a temperature ranging
from 100 to 150.degree. C. under reduced pressure to produce oligo
(lactic acid) with a weight-average molecular weight of at least 300 but
not greater than 1000 by dehydration-condensation;adding at least one
solvent selected from the group consisting of toluene, xylene,
mesitylene, ethylbenzene, and mineral spirit, to the fermentation liquor
which contains the oligo (lactic acid);heating the solvent added
fermentation liquor which contains the oligo (lactic acid) with agitaion
to a temperature ranging from 60.degree. C. to 150.degree. C. to dissolve
the oligo (lactic acid) in the heated solvent for extraction;stopping the
agitation while keeping the heating to separate the solvent in which the
oligo (lactic acid) is dissolved from the fermentation liquor; andcooling
down the separated solvent to near room temperature to collect the oligo
(lactic acid).

15. A method for producing oligo (lactic acid) from a lactic acid
fermentation liquor, comprising the steps of:heating a lactic acid
fermentation liquor with a pH of 4.8 or less to a temperature ranging
from 100 to 150.degree. C. under reduced pressure to produce oligo
(lactic acid) with a weight-average molecular weight of at least 300 but
not greater than 1000 by dehydration-condensation; andwashing the
fermentation liquor which contains the oligo (lactic acid) with water to
separate and collect the oligo (lactic acid) which is insoluble in the
water.

16. The method of claim 13, wherein cells are removed from the lactic acid
fermentation liquor.

17. An apparatus for producing oligo (lactic acid) from a lactic acid
fermentation liquor, comprising:starting material supply means for
supplying a lactic acid fermentation liquor with a pH of 4.8 or
less;solvent supply means for supplying a solvent selected from the group
consisting of oligo (lactic acid) extracting solvent and a washing
solvent, the oligo (lactic acid) extracting solvent being at least one
solvent selected from the group consisting of toluene, xylene,
mesitylene, ethylbenzene, and mineral spirit, and the washing solvent
being water;a reaction vessel that retains the supplied lactic acid
fermentation liquor and solvent with agitation;heating means for heating
the reaction vessel; andoligo (lactic acid) separating and collecting
means for separating and collecting oligo (lactic acid) from the reaction
vessel.

18. The apparatus of claim 17, further comprising cooling means for
condensing a vapor obtained from evaporation out of the reaction vessel.

19. The apparatus of claim 18, further comprising liquid separating means
for subjecting a liquid obtained from condensation by the cooling means
to gravity separation for refluxing a liquid with a lower specific
gravity to the reaction vessel and discharging water with a higher
specific gravity.

20. The apparatus of claim 17, further comprising decolorizing means for
decolorizing a liquid collected by the oligo (lactic acid) separating and
collecting means.

21. The method of claim 14, wherein cells are removed from the lactic acid
fermentation liquor.

22. The method of claim 15, wherein cells are removed from the lactic acid
fermentation liquor.

23. The apparatus of claim 18, further comprising decolorizing means for
decolorizing a liquid collected by the oligo (lactic acid) separating and
collecting means.

24. The apparatus of claim 19, further comprising decolorizing means for
decolorizing a liquid collected by the oligo (lactic acid) separating and
collecting means.

Description:

TECHNICAL FIELD

[0001]The present invention relates to methods for separating a lactic
acid component from a lactic acid fermentation liquor, and apparatuses
for the same.

BACKGROUND ART

[0002]Conventionally, a lactic acid component is separated from a lactic
acid fermentation liquor using, for example, a method for collecting a
lactic acid component in the form of a lactic acid ester, a method for
collecting a lactic acid component in the form of calcium lactate, or a
method for separating a lactic acid component by electrodialysis.

[0003]As the method for collecting a lactic acid component in the form of
a lactic acid ester, a method is disclosed in which a lactic acid ester
is synthesized by adding butanol or pentanol to ammonium lactate
generated by fermentation, and collected by distillation (for example,
Japanese Laid-Open Patent Publication No. 6-311886).

[0004]As the method for collecting a lactic acid component in the form of
calcium lactate, a method is disclosed in which lactic acid obtained from
fermentation is neutralized with calcium hydroxide or calcium carbonate
to generate calcium lactate precipitates for collection (for example,
Japanese Laid-Open Patent Publication No. 6-070679).

[0005]As the method using electrodialysis, a method is disclosed in which
a lactic acid fermentation liquor is introduced into a desalting chamber
of an electrodialysis cell with which an anode, a cathode, and
alternately arranged cation exchange membranes and anion exchange
membranes are provided, and thus salts of lactic acid is concentrated in
the fermentation liquor and separated (for example, Japanese Laid-Open
Patent Publication No. 7-155191).

[0006]Japanese Laid-Open Patent Publication Nos. 2002-300898 and 10-287668
disclose methods for producing polylactic acid from fermented lactic acid
products as a starting material. Japanese Laid-Open Patent Publication
No. 2002-300898 discloses a method for producing a polylactic acid by
esterifying ammonium lactate products from lactic acid fermentation with
an alcohol and polycondense them, and then producing lactides and
polymerizing them. Japanese Laid-Open Patent Publication No. 10-287668
discloses a method for producing lactide by heating ammonium lactate
under reduced pressure, and a method for producing a polylactic acid by
ammonia evaporation and dehydratively condensation-polymerization. All of
these methods are described as polymerization methods without converting
fermented lactic acid products (ammonium lactate salt) from a salt form
into a free form. Ammonium lactate is azeotropically dehydrated with
xylene to produce polylactic acid, and then polylactic acid with a
weight-average molecular weight of 70000 is treated with methylene
chloride and methanol for crystallization.

DISCLOSURE OF INVENTION

[0007]In conventional methods for separating a lactic acid component from
a lactic acid fermentation liquor, it is required to separate and purify
the lactic acid component by causing a reaction by adding a further
reaction reagent, for example, an alcohol such as butanol or pentanol, or
a calcium salt such as calcium hydroxide or calcium carbonate. Thus,
except for the case of obtaining lactic acid esters or calcium lactate as
a final target product, the further reagents may be used with increase in
the number of steps, the cost of agents, and the possibility of
incorporation of concomitant chemical substances or impurities. For
example, when a separated lactic acid component is used as a starting
material of chemicals such as polylactic acid or polyester polyol, it is
required to separate lactic acid esters produced in the reaction by
distillation, and then hydrolyze them to lactic acid as the pre-reaction
form. The resultant alcohols are required to be removed since alcohols
cannot be contained in the final product.

[0008]In the separation method using electrodialysis, there are a concern
about the life and fouling of the membranes used. Furthermore, a lactic
acid fermentation liquor may contain not only lactic acid, but also
organic components such as proteins and surfactants and inorganic
components such as salts of phosphoric acid, sulfuric acid, acetic acid,
and citric acid, as nutrients and medium components for lactic acid
bacteria. Thus, contamination of the membranes is severer, and
maintenance of the membranes leads to an increase in the cost. In
addition, salts derived from medium components in the fermentation
liquor, as well as the lactate salts, are concentrated by dialysis, and
thus the precision of separation and the purity of the lactate salt are
lowered.

[0009]According to the present invention made in view of these problems,
it is intended to provide a method for separating a lactic acid component
from a lactic acid fermentation liquor, which does not require reaction
reagents, which cause an increase in the cost or incorporation of
impurities, or consumables such as separation membranes, which are not
contained in a final product, and which includes a reduced number of
steps.

[0011]adding at least one solvent selected from the group consisting of
toluene, xylene, mesitylene, ethylbenzene, methanol, ethanol, propanol,
butanol, and mineral spirit, to a lactic acid fermentation liquor with a
pH of 4.8 or less; and

[0012]extracting a lactic acid component from the solvent added
fermentation liquor, at a temperature ranging from room temperature to
the boiling point of the solvent.

[0014]adding at least one solvent selected from the group consisting of
toluene, xylene, mesitylene, ethylbenzene, methanol, ethanol, propanol,
butanol, and mineral spirit, to a lactic acid fermentation liquor with a
pH of 4.8 or less;

[0015]heating the solvent added fermentation liquor to azeotropically
dehydrate the fermentation liquor; and

[0016]extracting a lactic acid component from the dehydrated fermentation
liquor, at a temperature ranging from room temperature to the boiling
point of the solvent.

[0018]heating a lactic acid fermentation liquor with a pH of 4.8 or less
to a temperature of not higher than 100° C. under reduced pressure
to dehydrate the fermentation liquor;

[0019]adding at least one solvent selected from the group consisting of
toluene, xylene, mesitylene, ethylbenzene, methanol, ethanol, propanol,
butanol, and mineral spirit, to the dehydrated fermentation liquor; and

[0020]extracting a lactic acid component from the solvent added
fermentation liquor, at a temperature ranging from room temperature to
the boiling point of the solvent.

[0022]adding at least one solvent selected from the group consisting of
toluene, xylene, mesitylene, ethylbenzene, and mineral spirit, to a
lactic acid fermentation liquor with a pH of 4.8 or less;

[0023]heating the solvent added fermentation liquor for azeotropy and then
to a temperature ranging from the azeotropic point of the solvent and
water to the boiling point of the solvent, whereby the fermentation
liquor is dehydrated and a lactic acid component in the fermentation
liquor is condensed to produce oligo (lactic acid) with a weight-average
molecular weight of not greater than 5000; and

[0024]heating the fermentation liquor which contains the oligo (lactic
acid) to a temperature ranging from 60° C. to the boiling point of
the solvent to extract the oligo (lactic acid) from the fermentation
liquor.

[0025]The present invention further provides a method for producing a
oligo (lactic acid) from a lactic acid fermentation liquor, comprising
the steps of:

[0026]heating a lactic acid fermentation liquor with a pH of 4.8 or less
to a temperature ranging from 100 to 150° C. under reduced
pressure to produce oligo (lactic acid) with a weight-average molecular
weight of at least 300 but not greater than 1000 by
dehydration-condensation; and

[0027]adding at least one solvent selected from the group consisting of
toluene, xylene, mesitylene, ethylbenzene, and mineral spirit, to the
fermentation liquor which contains the oligo (lactic acid); and

[0028]heating the solvent added fermentation liquor which contains the
oligo (lactic acid) to a temperature ranging from 60° C. to the
boiling point of the solvent to extract the oligo (lactic acid) from the
fermentation liquor.

[0030]heating a lactic acid fermentation liquor with a pH of 4.8 or less
to a temperature ranging from 100 to 150° C. under reduced
pressure to produce oligo (lactic acid) with a weight-average molecular
weight of at least 300 but not greater than 1000 by
dehydration-condensation; and

[0031]washing the fermentation liquor which contains the oligo (lactic
acid) with water to separate and collect the oligo (lactic acid) from the
fermentation liquor.

[0032]In an embodiment, cells are removed from the lactic acid
fermentation liquor.

[0033]Furthermore, the present invention provides an apparatus for
separating a lactic acid component from a lactic acid fermentation
liquor, comprising:

[0034]starting material supply means for supplying a lactic acid
fermentation liquor with a pH of 4.8 or less;

[0035]solvent supply means for supplying a solvent selected from the group
consisting of a lactic acid component extracting solvent and a washing
solvent, the lactic acid component extracting solvent being at least one
solvent selected from the group consisting of toluene, xylene,
mesitylene, ethylbenzene, methanol, ethanol, propanol, butanol, and
mineral spirit, and the washing solvent being water;

[0036]a reaction vessel that retains the supplied lactic acid fermentation
liquor and solvent with agitation; and

[0037]lactic acid component separating and collecting means for separating
and collecting a lactic acid component from the reaction vessel.

[0038]In an embodiment, the apparatus further comprises heating means for
heating the reaction vessel.

[0039]In a further embodiment, the apparatus further comprises cooling
means for condensing a vapor obtained from evaporation out of the
reaction vessel.

[0040]In a still further embodiment, the apparatus further comprises
liquid separating means for subjecting a liquid obtained from
condensation by the cooling means to gravity separation for refluxing a
liquid with a lower specific gravity to the reaction vessel and
discharging water with a higher specific gravity.

[0041]In a different embodiment, the apparatus further comprises
decolorizing means for decolorizing a liquid collected by the lactic acid
component separating and collecting means.

[0042]According to the present invention, a lactic acid component can be
separated from a lactic acid fermentation liquor with a simple process,
at a low cost, and without incorporation of impurities.

BRIEF DESCRIPTION OF DRAWINGS

[0043]FIG. 1 is a schematic view of a preferred example of an apparatus
according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0044]To complete the present invention, the pH of the lactic acid
fermentation liquor has been focused on for the separation of a lactic
acid component therefrom. The present invention is based on the findings
that at a lower value of pH, lactate ion become lactic acid due to shift
of dissociation equilibrium, or the condensation reaction of lactic acid
is accerelated to form oligomers, thereby facilitating extraction of the
lactic acid component with a solvent. Herein, the lactic acid component
refers to lactic acid and/or oligo (lactic acid).

Lactic Acid Fermentation Liquor

[0045]Herein, a lactic acid fermentation liquor refers to an aqueous
solution containing lactic acid produced from carbon sources such as
glucose that can be assimilated in fermentation by microorganisms such as
lactic acid bacteria. A lactic acid fermentation liquor may contain cells
of microorganisms such as lactic acid bacteria, lactic acid produced by
fermentation, a carbon source such as glucose that has not been
assimilated, byproducts (acetic acid, formic acid, etc.), medium
components as nutrients for the bacteria, and the like.

[0046]Lactic acid bacteria may be classified into four types, namely
bifidobacteria, enterococcus bacteria, lactobacillus bacteria, and
streptococcus bacteria. Lactic acid bacteria include bacteria of the
genus Streptococcus, the genus Lactobacillus, the genus Bifidohacterium,
the genus Lactococcus, the genus Pediococcus, and the genus Leuconostoc,
such as Streptococcus thermophilus, Streptococcus cremoris, Streptococcus
faecalis, Streptococcus lactis, Lactobacillus bulgaricus, Lactobacillus
acidophilus, Lactobacillus casei, Lactobacillus delbrueckii,
Lactobacillus arabinosus, Lactobacillus caucasicus, Lactobacillus lactis,
Lactobacillus Leishmanni, Lactobacillus musicus, Lactobaciflus
thermophilus, Lactobacillus plantarum, Bifidohacterium bifidum,
Bifidohacterium adolescentis, Bifidohacterium longum, Bifidohacterium
breve, Bifidohacterium infantis, Lactococcus lactis, Lactococcus
cremoris, Pediococcus damnosus, and Leuconostoc mesenteroides. Any
bacteria other than those known as lactic acid bacteria also can be used
for lactic acid fermentation, as long as they produce lactic acid, and
thus such bacteria also may be contained in the lactic acid fermentation
liquor. For example, yeast or Escherichia coli in which a lactate
dehydrogenase (LDH) gene is incorporated can be used. In view of
separation of the lactic acid component, bacteria that capable of
producing lactic acid alone (homolactic fermentation) are preferable.

[0048]Accordingly, the lactic acid fermentation liquor is a mixed aqueous
solution that contains many solutes, including lactic acid, and may be
colored yellow or orange to brown. In this mixed aqueous solution, the
concentration of lactic acid may be approximately 10 to 150 g/L.

[0049]In the method according to the present invention, prior to
separation of the lactic acid component, cells of microorganisms are
preferably removed from the lactic acid fermentation liquor. When cells
are removed in advance, impurities can be reduced in the subsequent
extraction. Since cells are insoluble in water, the cells can be removed
by allowing the lactic acid fermentation liquor to stand, and then
collecting supernatant, which can be used for the method according to the
present invention. Furthermore, the cells can be removed not by allowing
the lactic acid fermentation liquor to stand, but by subjecting the
lactic acid fermentation liquor to centrifugal separation or filtration.
With this operation, insoluble matter other than cells, such as
contaminants, also can be removed.

The pH of the Lactic Acid Fermentation Liquor

[0050]In the process of lactic acid fermentation, the pH of the
fermentation liquor is lowered due to the produced lactic acid, thereby
lowering the activity of microorganisms. Accordingly, fermentation is
usually performed with neutralization with an agent such as sodium
hydroxide, ammonia water, potassium hydroxide, calcium hydroxide, or
sodium carbonate. The pH may be adjusted to near neutral of 5.0 or more
in the process of lactic acid fermentation since many lactic acid
bacteria does not exhibit a strong ability for fermentation at a pH of
less than 5.0. The pKa of lactic acid is approximately 3.8, and thus,
when the lactic acid fermentation liquor is near neutral, lactic acid is
present in an almost dissociated state and in the form of lactate ions.
According to the chemical species of the agent used for neutralization,
there are counterions such as ammonium ions, sodium ions, potassium ions,
or calcium ions.

[0051]The lactic acid fermentation liquor for use in the method of the
present invention has a pH of 4.8 or less. Since the pKa of lactic acid
is approximately 3.8, at least 10 mol % or more of lactic acid is present
without dissociated and in the form of lactic acid in a lactic acid
fermentation liquor with a pH of 4.8. A comparison between the molecular
polarities of lactate ion and lactic acid shows that lactic acid has a
lower polarity than lactate ion, and thus can be more easily dissolved in
a solvent other than water. Furthermore, even if the content rate of
lactic acid is reduced, dissociation equilibrium can be shifted with
extraction of lactic acid to convert lactate ions that may be present in
the solution into lactic acid, thereby facilitating extraction of lactic
acid. The content rate of lactic acid is preferably increased, and thus,
the pH of the lactic acid fermentation liquor is more preferably 3.8 or
less. For example, at a pH of 3.8, approximately 50% is present in the
form of lactic acid, and thus the extraction efficiency is higher than at
a higher pH. A pH of 2.8 or less is still more preferable. At a pH of 2.8
or less, 90% or more is present in the form of lactic acid, and thus the
extraction efficiency becomes even higher.

[0052]As described above, the pH of the lactic acid fermentation liquor
can be usually near neutral of not less than 5.0 in the process of lactic
acid fermentation. When the pH of the lactic acid fermentation liquor is
greater than 4.8, the pH of the lactic acid fermentation liquor is
previously adjusted to 4.8 or less for the method of the present
invention. In order to adjust the pH to 4.8 or less, an acid can be
added. There is no specific limitation on an acid to be added, but acids
such as hydrochloric acid, sulfuric acid, carbonic acid, phosphoric acid,
and nitric acid are preferable. Furthermore, the fermentation liquor
neutralized with ammonia may be heated for lowering the pH. The
temperature and time for heating can be selected as appropriate by a
person skilled in the art. For example, the pH can be not greater than
4.8 by heating at 130° C. for 4 hours. Furthermore, the pH can be
lowered to 4.3 by heating at 150° C. for 6 hours.

[0053]When the pH of the lactic acid fermentation liquor is 4.8 or less,
the condensation reaction of lactic acid is facilitated. For example, in
the case of that the lactic acid fermentation liquor neutralized with
ammonia is heated at 150° C.: when the pH is 6 before pH
adjustment, lactic acid is hardly condensed; when the pH is adjusted to
4, 40% of lactic acid can be condensed; and when the pH is adjusted to
2.5, 90% or more of lactic acid can be condensed.

Extraction of the Lactic Acid Component Using the Solvent

[0054]In the method according to the present invention, the lactic acid
component can be extracted using at least one solvent selected from the
group consisting of toluene, xylene, mesitylene, ethylbenzene, methanol,
ethanol, propanol, butanol, and mineral spirit, which may be any solvent
for industrial use. The amount of solvent added to the fermentation
liquor can be selected as appropriate by a person skilled in the art
based on the description of the specification. Herein, the solvents are
also referred to as "lactic acid component extracting solvents" since
these solvents are used for extracting the lactic acid component.

[0055]Toluene, xylene, mesitylene, ethylbenzene, and mineral spirit are
solvents in which lactic acid or oligo (lactic acid) cannot be dissolved
at near room temperature, but lactic acid or oligo (lactic acid) can be
dissolved with heating. Therefore, by adding the solvents to the lactic
acid fermentation liquor, and heating them preferably with agitation,
lactic acid or oligo (lactic acid) can be taken from the lactic acid
fermentation liquor. Furthermore, in these solvents, lactic acid or oligo
(lactic acid) can be dissolved with heating, but not be dissolved at near
room temperature. Therefore, although lactic acid or oligo (lactic acid)
is dissolved in the solvents when heated, it becomes insoluble in the
solvents and is precipitated when cooled down to near room temperature,
thereby facilitating separation and collection of lactic acid or oligo
(lactic acid). Accordingly, by using the solvents, lactic acid or oligo
(lactic acid), or their mixture can be extracted by heating, and can be
readily collected just by cooling down.

[0056]The temperature at the extraction can be a temperature ranging from
60° C. to the boiling point of each solvent, and is preferably
150° C. or lower. Since the separation takes advantage of the
difference between the solubilities of the lactic acid component and the
other components (e.g., medium components) in the lactic acid
fermentation liquor, it is desirable that the temperature is such that it
can be avoided that the medium components and the like are modified to be
water-insoluble. For example, in MRS medium, which is a standard medium
for lactic acid bacteria, while the extent of medium components that
become water-insoluble by heating at 150° C. for 7 hours is
approximately 0.5 wt %, the extent is 1.5 wt % at 160° C., and
over 2 wt % at 180° C. Therefore, at a higher temperature, the
medium components may be modified to incorporate impurities at the
extraction. Thus, it is heated preferably at 150° C. or lower. For
example, in the case of xylene, extraction can be performed by heating to
a temperature ranging from 60 to 139° C. (the boiling point of
m-xylene). Toluene has a boiling point of 110° C., mesitylene has
a boiling point of 164.7° C., ethylbenzene has a boiling point of
136° C., and mineral spirit has a boiling point of 150° C.
In a case where each solvent is used alone, the heating temperature may
be a temperature ranging from 60° C. to the boiling point of the
solvent. When the boiling point is higher than 150° C., the
heating temperature is preferably 150° C. or lower. In a case
where the solvents are used in combination, it is desirable that the
temperature is set in consideration of the azeotropic point of the
combined solvents and water.

[0057]Methanol, ethanol, propanol, and butanol also can be used for
extracting the lactic acid component, in consideration of the solubility
of lactic acid in these solvents. While lactic acid has a good solubility
in methanol, ethanol, propanol, and butanol, the medium components
contained in the lactic acid fermentation liquor and the agents for use
in neutralization or acidification have a poor solubility in these
solvents. The propanol may be either one of 1-propanol (n-propanol) and
2-propanol (isopropanol). The butanol may be any one of 1-butanol
(n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol),
and 2-methyl-2-propanol (tertbutanol).

[0058]Here, all of the medium components are soluble in water, but few
components among the medium components are soluble in a lower alcohol.
For example, in the case of a standard medium M17 for lactic acid
fermentation, 100% of the medium components are dissolved in water, but
33.8% of the medium components are soluble in methanol, 5.1% in ethanol,
3.8% in isopropanol, and 4.5% in butanol, that is, the proportion of
those that are soluble in these alcohols is small.

[0059]Furthermore, the fermentation liquor also may contain salts of an
alkali used for neutralization and an acid added for acidification.
Examples thereof include ammonium sulfate, sodium sulphate, ammonium
chloride, and sodium chloride. Depending on the concentration of lactic
acid, these salts may be contained in an amount larger than that of the
medium components in the fermentation liquor. These salts are soluble in
water, but insoluble or poorly soluble in alcohols such as methanol,
ethanol, propanol, or butanol, and thus the amount of soluble matter
other than lactic acid is slight.

[0060]By adding, to the lactic acid fermentation liquor containing the
medium components and the salts of an alkali for neutralization and an
acid for acidification in the dissolved states, an alcohol such as
methanol, ethanol, propanol, or butanol, which functions as a poor
solvent, preferably with agitation, contaminants such as the medium
components and the like can become insoluble therein and be precipitated,
and the lactic acid component can be collected in the form of liquid.

[0061]When the content rate of water in the fermentation liquor is reduced
by dehydration in advance, the effect of the alcohol functioning as a
poor solvent is increased. Therefore, the increased amount of
contaminants is precipitated, and thus the increased extent of solutes
other than lactic acid is removed from the fermentation liquor to yield
lactic acid with a lower amount of impurities.

[0062]Conversely, it is difficult to perform distillation separation and
the like after the extraction using an alcohol with 5 or more carbon
atoms since it has a high boiling point. For example, while methanol has
a boiling point of 65° C., ethanol has a boiling point of
78° C., n-propanol has a boiling point of 97° C.,
isopropanol has a boiling point of 82° C., isobutanol has a
boiling point of 108° C., tertbutanol has a boiling point of
82.5° C., 2-butanol has a boiling point of 100° C., and
1-butanol has a boiling point of 118° C., the boiling points of
isomers of pentanol are 112 to 137° C., except that
2-methyl-2-butanol has a boiling point of 102° C. Furthermore, the
cost of these alcohols is higher than that of a low molecular weight
alcohol.

[0063]The temperature at the extraction can be a temperature ranging from
room temperature to the boiling point of each solvent. For example, in
the case of ethanol, extraction can be performed at a temperature ranging
from room temperature to 78° C. Furthermore, in a case where the
solvents are used in combination, it is desirable that the temperature is
set in consideration of the azeotropic point of the combined solvents and
water.

Dehydration of the Lactic Acid Fermentation Liquor by Azeotropy with the
Solvent

[0064]When the lactic acid fermentation liquor is dehydrated, the amount
of solvent water is reduced, thereby facilitating dissolution and
extraction of the lactic acid component by the solvent. Thus, the
dehydration is preferably performed prior to extracting the lactic acid
component. The dehydration may be performed simultaneously with
extraction of the lactic acid component.

[0065]All of the lactic acid component extracting solvents, namely
toluene, xylene, mesitylene, ethylbenzene, methanol, ethanol, propanol,
butanol, and mineral spirit, are solvents that can form an azeotropic
mixture with water. Accordingly, when the lactic acid fermentation liquor
to which any of these solvents has been added is heated at least to the
azeotropic point of the solvent and water, water can be evaporated out of
the reaction system to dehydrate the lactic acid fermentation liquor. The
heating is performed preferably with agitation.

[0066]Among the lactic acid component extracting solvents, toluene,
xylene, mesitylene, ethylbenzene, and mineral spirit, that have a
specific gravity smaller than 1 and are water-insoluble, can be separated
from water based on the specific gravities. When the solvent is heated
together with water to the azeotropic point or higher, then the azeotrope
of the water and solvent is evaporated out, and subsequently the
azeotrope is cooled down, then the azeotrope is condensed into a liquid.
The liquid can be separated into water and the solvent due to the
difference between the specific gravities of the solvent and water. Water
is removed off, while the solvent is circulated and reused in the
reaction system. More specifically, the azeotrope of water and the
solvent evaporated out of a reaction vessel by heating is condensed in a
cooling tube, introduced into a water separator, and separated into water
and the solvent at the lower layer and the upper layer, respectively,
based on the difference in the specific gravities. For this purpose, the
reaction vessel that has an opening for discharging a vapor is preferably
provided with heating means, a cooling tube, and a water separator such
as a decanter or a Dean-Stark trap. According to the water separator,
water at the lower layer can be removed out of the system, and the
solvent at the upper layer can be refluxed and circulated in the reaction
vessel. Accordingly, the lactic acid fermentation liquor can be
dehydrated without consumption or leakage of the solvent.

[0067]The temperature for heating at the azeotropy can be a temperature
ranging from the azeotropic point of each solvent and water to the
boiling point of the solvent. As described above, at a higher
temperature, the medium components may be modified to incorporate
impurities at the extraction. Thus, it is heated preferably at
150° C. or lower. For the dehydration, it is preferably heated at
the azeotropic point or higher (e.g., preferably 90 to 150° C.)
for a time suitable for removing water from the fermentation liquor
(e.g., 1 to 5 hours). In the case of toluene, xylene, mesitylene,
ethylbenzene, or mineral spirit, lactic acid or oligo (lactic acid), or a
mixture of lactic acid and oligo (lactic acid) can be dissolved in these
solvents and thus collected.

[0068]Furthermore, in the case of alcohols of methanol, ethanol, propanol,
and butanol, after the lactic acid fermentation liquor is azeotropically
dehydrated, these alcohols may be used to dissolve and collect lactic
acid. The lactic acid fermentation liquor may be azeotropically
dehydrated in a batch with addition of the alcohol in an excessive amount
relative to the amount of water in the lactic acid fermentation liquor,
to dissolve lactic acid in the remaining alcohol and collect it.
Alternatively, the lactic acid fermentation liquor may be azeotropically
dehydrated with continuous addition of the alcohol, to dissolve lactic
acid in an added alcohol after the azeotropical dehydration and collect
it. As the alcohol for addition to the lactic acid fermentation liquor,
an alcohol may be separated from the azeotropic mixture and added again
to the lactic acid fermentation liquor, or alternatively an alcohol may
be newly added.

Dehydration of the Lactic Acid Fermentation Liquor by Heating under
Reduced Pressure

[0069]The dehydration of the lactic acid fermentation liquor as described
above may be performed also by heating under reduced pressure.

[0070]The heating temperature is not higher than 100° C.,
preferably 40 to 100° C. At a temperature of higher than
100° C., the polymerization of lactic acid may be developed in the
fermentation liquor. At a temperature of lower than 40° C., the
vapor pressure is lower than 55 mmHg, and the speeds of dehydration and
drying considerably may be lowered even under the reduced pressure.

[0071]The pressure is preferably reduced to 1 to 100 torr (i.e.,
approximately 133 Pa to approximately 13300 Pa). At a pressure of higher
than 100 torr (approximately 13300 Pa), the time required for dehydration
and drying may become longer even with heating. At a pressure of lower
than 1 torr (approximately 133 Pa), not only water but also some of
lactic acid may be removed by evaporation.

[0072]For dehydration of the lactic acid fermentation liquor, it is
preferable that the heating temperature is not higher than 100°
C., preferably 40 to 100° C., and the pressure is reduced to 1 to
100 torr (i.e., approximately 133 Pa to approximately 13300 Pa). The time
for heating under reduced pressure can be determined as appropriate
according to the heating temperature and the pressure after reduction.
The heating under reduced pressure may be performed while changing the
heating temperature and the pressure after reduction several times in a
stepwise manner. For example, the lactic acid fermentation liquor can be
heated to 50° C., and kept under a reduced pressure of 10 torr
(approximately 1330 Pa) for 2 hours, and then under a reduced pressure of
5 torr (approximately 670 Pa) for 2 hours for dehydration.

Production of the Oligo (Lacetic Acid) by Azeotropy with the Solvent
(Dehydration-Condensation)

[0073]With development of the dehydration of the lactic acid fermentation
liquor, the condensation reaction of lactic acid can be developed to
produce oligo (lactic acid). Since the oligomerized lactic acid has a
further lowered polarity, the difference between the solubilities of the
lactic acid and the other components, including medium, in the
fermentation liquor is increased, thereby facilitating extraction of
lactic acid using toluene, xylene, mesitylene, ethylbenzene, and mineral
spirit, among the lactic acid component extracting solvents.

[0074]Since there are a carboxyl group and a hydroxyl group in one
molecule of lactic acid, lactic acids can be homopolymerized by
condensation. By discharging water from the polymerization out of the
system, the degree of polymerization can be further increased. According
to the present invention, such a polymerization of lactic acid is
preferable that the weight-average molecular weight is not greater than
5000. At weight-average molecular weight of greater than 5000, the
solubility may be lowered in the solvent when heated. Furthermore, it
takes a considerably longer time for dehydration-condensation to obtain a
weight-average molecular weight of greater than 5000 than that for
extraction or dehydration. In the case, the medium components and the
like in the fermentation liquor may be deteriorated with heating to
modify their solubility, and thus the separation by extraction may be
poorly performed.

[0075]Also in a dehydration-condensation reaction, the temperature for
heating at the azeotropy can be a temperature ranging from the azeotropic
point of each solvent and water to the boiling point of the solvent. It
is more important to separate oligo (lactic acid) from the other
components (e.g., medium components) in the lactic acid fermentation
liquor based on the solubilities, rather than to increase the degree of
polymerization of lactic acid. More specifically, a difference is to be
provided between the solubilities of a lactic acid component and the
other components (e.g., medium components) in the lactic acid
fermentation liquor by oligomerizing lactic acid. Accordingly, it is
desirable that the temperature is such that it can be avoided that the
medium components and the like would be modified to be insoluble in
water. At a higher temperature, the medium components may be modified to
be incorporated as impurities at the extraction. Thus, it is heated
preferably at 150° C. or lower. For the dehydration-condensation,
it is preferably heated at the azeotropic point or higher (e.g.,
preferably 90 to 150° C.) for a time suitable for removing water
from the fermentation liquor (e.g., 1 to 5 hours), and while keeping a
temperature ranging from the azeotropic point to the boiling point of the
solvent (note that the temperature is 150° C. or lower), heated
for a time suitable for producing an oligomer with a weight-average
molecular weight of not greater than 5000 (e.g., 5 to 24 hours). By
further applying the heating on a lactic acid fermentation liquor in
which the content rate of water is reduced by dehydration, the
condensation reaction of lactic acid can be developed to produce oligo
(lactic acid).

[0076]The oligo (lactic acid) produced by dehydration-condensation is
extracted using the lactic acid component extracting solvents (i.e., at
least one solvent selected from the group consisting of toluene, xylene,
mesitylene, ethylbenzene, and mineral spirit) as described above. In the
process of heating (e.g., heating to the boiling point of the solvent)
for the dehydration-condensation reaction using the solvent, the
extraction process may be performed simultaneously.

Production of the Oligo (Lactic Acid) by Heating under Reduced Pressure
(Dehydration-Condensation)

[0077]The oligomerization of lactic acid may be performed by heating under
reduced pressure. The temperature for heating is preferably in a range of
100 to 150° C. At a temperature for heating of lower than
100° C., the polymerization reactivity of lactic acid may be
poorer and thus the extent for conversion of lactic acid to oligomer may
be lower. At a temperature for heating of higher than 150° C., the
medium components may be deteriorated as described above.

[0078]In the case of polymerization by heating under reduced pressure,
lactide may be generated during the polymerization of lactic acid.
Lactide is generated via the depolymerization reaction of the oligo
(lactic acid), and may be an impurity in which two molecules of lactic
acid are cyclically associated. In particular, at a higher temperature,
or at a higher degree of vacuum, lactide would be generated, and the
generated lactide may be sublimated out of the system, thereby lowering
the yield of oligo (lactic acid). Accordingly, it is preferable that the
heating temperature is 100 to 150° C., and the pressure is reduced
to 10 to 100 torr (i.e., approximately 1330 Pa to approximately 13300
Pa). At a pressure of higher than 100 torr (approximately 13300 Pa), the
content rate of water may be increased in the system to prevent the
condensation. At a pressure of lower than 10 torr (approximately 1330
Pa), lactide may be more generated and sublimated off, thereby lowering
the yield of oligo (lactic acid) for separation and collection.

[0079]The oligo (lactic acid) produced by heating under reduced pressure
can be separated and collected from extraction by heating using at least
one solvent selected from the group consisting of toluene, xylene,
mesitylene, ethylbenzene, and mineral spirit, among the lactic acid
component extracting solvents. The temperature at the extraction by
heating is as described above.

[0080]The oligo (lactic acid) produced by heating under reduced pressure
also can be collected as insoluble in water, by washing the lactic acid
fermentation liquor subjected to heating under reduced pressure with
water, and dissolving the medium components in water and removing them.
Distilled water or deionized water is preferably used. The amount of
water for use in washing can be selected as appropriate by a person
skilled in the art based on the description of the specification. The
oligo (lactic acid) produced by heating under reduced pressure is
insoluble in water, but the medium components and the like in the lactic
acid fermentation liquor are soluble in water. Accordingly, when the
lactic acid fermentation liquor is washed with water (e.g., water is
added to the lactic acid fermentation liquor, the mixture is agitated,
followed by under solid-liquid separation such as still standing or
centrifugal separation), only the medium components are dissolved in
water, and thus the oligo (lactic acid), which is insoluble in water, can
be separated and collected. The temperature of water at washing can be
adjusted in a range from room temperature to the boiling point of water
(100° C.). It should be noted that the medium components recovered
by washing with water can be used again in a medium for the fermentation.

[0081]In the case of polymerization by heating under reduced pressure, the
weight-average molecular weight of the obtained oligo (lactic acid) is
preferably at least 300 but not greater than 1000. At weight-average
molecular weight of greater than 1000, sublimation lactide may be
generated via depolymerization, thereby lowering the yield of oligo
(lactic acid). At weight-average molecular weight of less than 300, the
solubility in the solvent may be lowered compared with that of 300 or
more, thereby lowering the efficiency of extraction by heating.
Furthermore, oligo (lactic acid), when the solubility in the solvent is
lowered, may be more transferred into water at the water washing, thereby
lowering the efficiency of the washing. Accordingly, the heating under
reduced pressure is performed preferably at a heating temperature of 100
to 150° C. and a reduced pressure of 20 to 100 torr (i.e.,
approximately 2700 Pa to approximately 13300 Pa), and in such a manner
that the weight-average molecular weight of the produced oligo (lactic
acid) is at least 300 but not greater than 1000. The time for the heating
under reduced pressure can be determined as appropriate according to the
temperature for heating and the pressure after reduction. The heating
under reduced pressure may be performed while changing the heating
temperature and the pressure after reduction several times in a stepwise
manner. For example, the lactic acid fermentation liquor can be heated to
150° C., and kept under atmospheric pressure for 2 hours, under a
reduced pressure of 100 torr (approximately 13300 Pa) for 2 hours, and
then under a reduced pressure of 30 torr (approximately 4000 Pa) for 2
hours for the dehydration-condensation of lactic acid.

The Separated Lactic Acid Component

[0082]The lactic acid component (e.g., lactic acid and oligo (lactic
acid)) separated from the lactic acid fermentation liquor through the
various processes as described above is collected and can be
appropriately used as a starting material for synthesizing compounds such
as polylactic acid, polyurethane, or polyol ester.

[0083]To a liquid that contains the produced lactic acid or oligo (lactic
acid) without cooling down, a catalyst (e.g., tin, tin oxide,
toluenesulfonic acid, tin chloride, etc.) can be added, and the mixture
can be heated continuously to develop the dehydrative polymerization in
the solvent, resulting in polylactic acid of a higher molecular weight.
The resultant liquid from extraction using the solvent contains only a
small amount of coexisting components such as the fermentation medium,
thereby facilitating forming that of a higher molecular weight.

Separation Apparatus

[0084]The present invention provides an apparatus for separating a lactic
acid component from a lactic acid fermentation liquor. The apparatus
includes: starting material supply means for supplying a lactic acid
fermentation liquor with a pH of 4.8 or less; solvent supply means for
supplying a solvent selected from the group consisting of a lactic acid
component extracting solvent and a washing solvent, the lactic acid
component extracting solvent being at least one solvent selected from the
group consisting of toluene, xylene, mesitylene, ethylbenzene, methanol,
ethanol, propanol, butanol, and mineral spirit, and the washing solvent
being water; a reaction vessel that retains the supplied lactic acid
fermentation liquor and solvent with agitation; and lactic acid component
separating and collecting means for separating and collecting a lactic
acid component from the reaction vessel. In one embodiment, the apparatus
may further include heating means for heating the reaction vessel, and
can facilitate the production of oligo (lactic acid) by dehydration or
dehydration-condensation in the lactic acid fermentation liquor. The
apparatus may further include cooling means for condensing a vapor from
evaporation out of the reaction vessel. The apparatus may further include
liquid separating means for subjecting a liquid from condensation by the
cooling means to gravity separation for refluxing a liquid with a lower
specific gravity to the reaction vessel and discharging water with a
higher specific gravity.

[0085]With this configuration, the solvent can be circulated and reused,
by extraction and by heating when heating is performed. Thus, safety and
low cost can be achieved without leakage or consumption of the solvent.

[0086]Then, an apparatus for separating a lactic acid component from a
lactic acid fermentation liquor according to the present invention will
be described with reference to FIG. 1, which shows an embodiment. FIG. 1
shows the configuration of an apparatus suitable for a method for
separating a lactic acid component by azeotropical dehydration and
azeotropical condensation. Note that in order to separate a lactic acid
component from a lactic acid fermentation liquor, not all the constituent
elements shown in FIG. 1 are required.

[0087]A reaction vessel 4 is configured to be capable of retaining a
lactic acid fermentation liquor and a solvent, which may be separated
from each other when allowed to stand, and agitating to mix the lactic
acid fermentation liquor and the solvent with heating if necessary. The
reaction vessel 4 may include agitator blades 2 that are rotated by an
agitator motor 1. The reaction vessel 4 may further include heating means
(e.g., a heater 3) for heating the reaction vessel, if necessary.

[0088]Starting material supply means includes a lactic acid fermentation
liquor tank and a pH adjusting vessel 5 that is connected to the tank.
The Starting material supply means is configured to supply the lactic
acid fermentation liquor, pH of which is adjusted to 4.8 or less at the
pH adjusting vessel 5, via a liquid sending pump 6 to the reaction vessel
4.

[0089]Solvent supply means includes a solvent tank, and is configured to
supply the solvent via a liquid sending pump 7 to the reaction vessel 4.
In an embodiment where the lactic acid component extracting solvent is
used to separate and collect a lactic acid component, the solvent supply
means includes a solvent tank that contains at least one solvent selected
from the group consisting of toluene, xylene, mesitylene, ethylbenzene,
methanol, ethanol, propanol, butanol, and mineral spirit. In a case where
two or more types of solvents are used, the solvent supply means may be
configured to send these solvents separately, or may be configured to
send these solvents in a mixed state.

[0090]In an embodiment where a lactic acid fermentation liquor subjected
to pH adjustment and heating under reduced pressure is washed with water
inside the reaction vessel 4, the solvent supply means may supply water
as a washing solvent to the reaction vessel 4.

[0091]In the apparatus according to the present invention, as the solvent
supply means, a solvent tank that supplies a lactic acid component
extracting solvent and a solvent tank that supplies water may be arranged
in parallel.

[0092]Lactic acid component separating and collecting means refers to any
means for separating and collecting a lactic acid component after
stopping agitation in the reaction vessel 4. In order to separate a
lactic acid component from a lactic acid fermentation liquor, separation
by stopping agitation of the agitator blades 2 arranged in the reaction
vessel 4 is used. When the lactic acid component extracting solvent is
used to separate and collect a lactic acid component, the lactic acid
component can be contained in a separated liquid with a lower specific
gravity (the upper layer). When water is used as the washing solvent to
separate and collect a lactic acid component, the lactic acid component
cannot be contained in a separated liquid with a lower specific gravity
(the upper layer), but the lactic acid component can be precipitated.

[0093]In an embodiment where the lactic acid component extracting solvent
is used to separate and collect a lactic acid component, a liquid which
contains the lactic acid component, which is separated by stopping
agitation in the reaction vessel, is collected for separation and
collection of the lactic acid component. For example, a pipe 14 is
provided at the upper portion of the reaction vessel 4 and connected to a
purifier 13. More specifically, agitation by the agitator blades 2
arranged in the reaction vessel 4 is stopped, and a separated liquid with
a lower specific gravity (the upper layer) by stopping the agitation is
sent from the upper portion of the reaction vessel 4 via the pipe 14 to
the purifier 13. At the purifier 13, a lactic acid component dissolved in
the supplied liquid can be separated and collected.

[0094]At the purifier 13, in order to separate and collect a lactic acid
component, either solid-liquid separation or solvent removal by
evaporation may be used according to the solvent used to extract the
lactic acid component.

[0095]When toluene, xylene, mesitylene, ethylbenzene, or mineral spirit is
used as the lactic acid component extracting solvent, a liquid collected
in the purifier 13 is cooled down to precipitate a dissolved component in
the liquid, and subjected to a separation technique such as still
standing or centrifugal separation. The solid component, which has been
dissolved, and liquid component are collected, while the solvent of
supernatant can be circulated into the reaction vessel. In this case, the
purifier 13 preferably has cooling means (not shown), and thus the solute
of the content in the purifier 13 is precipitated by this cooling
function, and the supernatant of the content in the purifier 13 is
introduced via a pipe 15 into a solvent supply line. As a valve used for
a discharge pipe (not shown) of the purifier 13, a ball valve is
preferable because a slurry or solid component flows therethrough.

[0096]When methanol, ethanol, propanol, or butanol is used as the lactic
acid component extracting solvent, the solvent, which is contained in a
liquid collected in the purifier 13, is removed by evaporation, and the
liquid from which the solvent has been removed can be collected from the
purifier 13. In this case, the purifier 13 preferably has an evaporator
or the like device (not shown), and thus, at the purifier 13, while the
extracting solvent can be removed off from the collected liquid by the
device, the desired solute can be collected in the form of liquid. Also,
means for solid-liquid separation on the collected liquid using a
separation technique such as still standing or centrifugal separation may
be provided. If insolubles are present in the collected liquid, the
insolubles can be also removed by this means. The solvent removed out of
the purifier 13 may be liquefied through the pipe 15 to be introduced
into the solvent supply line. Accordingly, the pipe 15 preferably
includes a device (e.g., cooling device) (not shown) that liquefies an
evaporated solvent.

[0097]A discharge pipe 16 is provided at the vessel bottom portion of the
reaction vessel 4, and is configured to be capable of discharging
precipitates (e.g., a solid component precipitated by loading an alcohol
solvent) or the like in the reaction vessel 4.

[0098]In an embodiment where a lactic acid fermentation liquor subjected
to pH adjustment and heating under reduced pressure is washed with water,
the produced oligo (lactic acid) can be obtained in the reaction vessel 4
while removing a supernatant aqueous solution with a lower specific
gravity separated following stopping agitation in the reaction vessel 4.
In this embodiment, stopping of agitation of the agitator blades 2
arranged in the reaction vessel 4 is mainly used for collecting a lactic
acid component. A pipe provided at the upper portion of the reaction
vessel 4 can be used for discharging the separated supernatant aqueous
solution with a lower specific gravity (containing dissolved medium
components and the like), and a pipe or collecting port (not shown) may
be provided at the lower portion or the bottom portion of the reaction
vessel 4 such that is configured to be capable of collecting the oligo
lactic acid). In this embodiment, the pipe 14 in communication with the
purifier 13 may be used as the pipe for discharging the supernatant
aqueous solution with a lower specific gravity.

[0099]The cooling means is a means for cooling down a vapor that is
obtained from evaporation out of the reaction vessel 4 and includes water
and the solvent. Examples thereof include water-cooling, air-cooling,
evaporative, or other condensers. For example, as a water-cooling
condenser, a condenser having the structure of shell-and-tube,
double-tube, or the like is used. The liquid separating means is a means
by which a liquid obtained from cooling down and condensation by the
cooling means is separated into water and the solvent for discharge water
and returning the solvent into the system. Examples thereof include water
separators such as a decanter and a Dean-Stark trap. More specifically, a
condenser 9 and a decanter 10 are connected via a distillation column 8
to the reaction vessel 4. A vapor from the reaction vessel 4 by heating
is rectified in the distillation column 8, and then a liquid obtained
from cooling down and condensation by the condenser 9 flows down to the
decanter 10. In the decanter 10, water and the solvent are separated to
form two layers due to the difference in specific gravities. The upper
solvent layer is refluxed via a U-tube 11 to the distillation column 8,
and the lower water layer is discharged by discharge means (not shown).
Furthermore, the liquid obtained from condensation in the distillation
column 8 flows down, and then is circulated via a U-tube 12 to the
reaction vessel 4.

[0100]The distillation column 8 may be an empty column, or may be filled
with Raschig rings, Lessing rings such as Dixon packings, Pall rings,
saddles such as McMahon packings, Sulzer packings, or other fillers.
Furthermore, the outer wall of the distillation column 8 may be
heat-sealed with glass wool or the like.

[0101]Since a mixture of water and the solvent is cooled down in the
condenser 9, the cooling is performed preferably at 0° C. or
higher and room temperature or lower. The cooling is performed more
preferably at 2 to 10° C. in order to increase the ability to cool
down and condense into a liquid. Any condenser may be used as the
condenser 9, as long as the vapor pipe can be cooled down from the
outside at its contact face, and examples thereof include a Liebig
condenser, an Allihn condenser, and a Liebig-Graham condenser.

[0102]The decanter 10 may be cooled down in order to increase the
efficiency of separation of a mixed liquid based on the difference in
specific gravities.

[0103]The apparatus may further include decolorizing means for
decolorizing a liquid collected by the lactic acid component separating
and collecting means. An absorbent such as activated carbon or activated
clay may be used for the decolorization. More specifically, the
decolorizing means includes: a column which is filled with the absorbent
and through which the collected liquid can pass; and loading the
absorbent into the collected liquid followed by separating and removing
the loaded absorbent. For example, the liquid can be decolorized by
passing through the column. Alternatively, the liquid can be decolorized
by being mixed with the absorbent, and subjected to solid-liquid
separation such as filtration or centrifugal separation.

[0104]The containers and the pipes are made of, for example, stainless
steel, glass, or resin such as Teflon (registered trade name).

[0105]Then, the operating process of a method for separating a lactic acid
component using the apparatus will be described.

[0106]In one embodiment, a lactic acid fermentation liquor, pH of which is
adjusted to 4.8 or less by addition of an acid at the pH adjusting vessel
5, is supplied via the liquid sending pump 6 to the reaction vessel 4. A
solvent is supplied from the solvent tank via the liquid sending pump 7
to the reaction vessel 4. In the reaction vessel 4, the lactic acid
fermentation liquor and the solvent are suspended by agitation of the
agitator blades 2 that are rotated by the agitator motor 1. If necessary,
the content in the reaction vessel 4 is heated by the heater 3.
Subsequently, the agitation is stopped and the content is allowed to
stand, while continuing heating if heating is performed. The resultant
supernatant of the content in the reaction vessel 4 is supplied via the
pipe 14 to the purifier 13. The lactic acid component in the content is
separated and collected at the purifier 13. In this manner, the lactic
acid component is separated and collected from the lactic acid
fermentation liquor.

[0107]In an embodiment where methanol, ethanol, propanol, or butanol is
used as the lactic acid component extracting solvent in order to collect
the lactic acid component in the purifier 13, the solvent is removed by
evaporation, by heating to a temperature ranging from room temperature to
the boiling point of the solvent, while the pressure is reduced by a
vacuum pump (not shown) attached to the purifier 13, for example, to 0.5
to 500 torr (i.e., approximately 67 Pa to approximately 67000 Pa). Since
methanol, ethanol, and propanol have a high vapor pressure, the solvent
also can be removed by evaporation, by heating at least to the boiling
point of the solvent under ambient pressure. The remaining liquid is
collected to obtain a lactic acid component in the form of liquid. If
insolubles are present in the collected liquid, solid-liquid separation
may be performed on the collected liquid using a separation technique
such as still standing or centrifugal separation, and thus, a transparent
liquid can be collected. The solvent removed off by evaporation may be
liquefied through the pipe 15, to which a cooling device is attached if
necessary, and supplied again as the extracting solvent via the liquid
sending pump 7 to the reaction vessel 4.

[0108]In an embodiment where toluene, xylene, mesitylene, ethylbenzene, or
mineral spirit is used as the lactic acid component extracting solvent,
the content in the purifier 13 is cooled down by the cooling device (not
shown) to precipitate the solute of the content, and the precipitated
lactic acid component is collected. In this manner, the lactic acid
component is separated from the lactic acid fermentation liquor.
Furthermore, the supernatant of the content in the purifier 13 is
introduced via the pipe 15 into the solvent supply line, and sent back to
the reaction vessel 4.

[0109]In a different embodiment, a lactic acid fermentation liquor, pH of
which is adjusted to 4.8 or less by addition of an acid at the pH
adjusting vessel 5, is supplied via the liquid sending pump 6 to the
reaction vessel 4. A solvent is supplied from the solvent tank via the
liquid sending pump 7 to the reaction vessel 4. In the reaction vessel 4,
the lactic acid fermentation liquor and the solvent are suspended by
agitation of the agitator blades 2 that are rotated by the agitator motor
1. The content in the reaction vessel 4 is heated by the heater 3. When
the content in the reaction vessel 4 is heated at least to the azeotropic
point of water and the solvent (e.g., 90° C. or higher), the
content starts to be evaporated. The vapor from evaporation passes
through the distillation column 8, and is cooled down and condensed at
the condenser 9, and flows down to the decanter 10. The condenser 9 (or
the condenser 9 and the decanter 10) is cooled down with circulating
chilled water or the like. In the decanter 10, the condensate is
separated into the solvent and water at the upper layer and at the lower
layer, respectively, due to the difference in specific gravities because
the solvent and water are not miscible. The solvent at the upper layer
flows back via the U-tube 11 to the distillation column 8. Because of the
pipe for the return path of U-shaped, the effect of water removal is
further increased. The solvent that has flowed back is refluxed together
with a solvent that is refluxed in the distillation column 8, to be
refluxed via the U-tube 12 to the reaction vessel 4. The reaction vessel
4 is heated continuously until most of the water in the supplied
fermentation liquor is removed, and then the agitation is stopped and the
content is allowed to stand while continuing the heating (the heating
temperature may be the same or may be changed). The resultant supernatant
of the content in the reaction vessel 4 is supplied via the pipe 14 to
the purifier 13. A lactic acid component in the content is separated and
collected at the purifier 13. The lactic acid component is separated and
collected at the purifier 13 as described above.

[0110]In an embodiment where methanol, ethanol, propanol, or butanol is
used as the lactic acid component extracting solvent, lactic acid can be
collected by azeotropically dehydrating the lactic acid fermentation
liquor without reflux of the solvent, and then dissolving the
azeotropically dehydrated lactic acid fermentation liquor in the solvent.
This is because the solvent and water are miscible and cannot be
separated even at the decanter 10. The lactic acid fermentation liquor
may be azeotropically dehydrated in a batch by addition of the alcohol in
an excessive amount relative to the amount of water in the lactic acid
fermentation liquor, and then in the remaining alcohol, lactic acid may
be dissolved for collection. Alternatively, the lactic acid fermentation
liquor may be azeotropically dehydrated by continuous addition of the
alcohol, and then in an alcohol added after the azeotropical dehydration,
lactic acid may be dissolved for collection. As the alcohol for addition
to the lactic acid fermentation liquor, an alcohol may be separated from
the azeotropic mixture and added again to the lactic acid fermentation
liquor, or alternatively an alcohol may be newly added.

[0111]In a still different embodiment, a lactic acid fermentation liquor,
pH of which is adjusted to 4.8 or less by addition of an acid at the pH
adjusting vessel 5, is supplied via the liquid sending pump 6 to the
reaction vessel 4. Then, the reaction vessel 4 is heated by the heater 3
for an appropriate time (preferably 1 to 10 hours) to a temperature of
not higher than 100° C., preferably to a temperature of 40 to
100° C., while the pressure in the reaction vessel 4, the
distillation column 8, and pipes connecting these constituent elements is
reduced, for example, to 1 to 100 torr (i.e., approximately 133 Pa to
approximately 13300 Pa), by the vacuum pump (not shown) connected to the
condenser 9. The content in the reaction vessel 4 starts to be
evaporated. The vapor from evaporation passes through the distillation
column 8, and is cooled down and condensed at the condenser 9. The water
from condensation is discharged from the pipe. The condenser 9 is cooled
down with circulating chilled water or the like. Accordingly, the lactic
acid fermentation liquor in the reaction vessel 4 is dehydrated.
Subsequently, the solvent is supplied from the solvent tank via the
liquid sending pump 7 to the reaction vessel 4. In the reaction vessel 4,
the dehydrated lactic acid fermentation liquor and the solvent are
agitated by the agitator blades 2 that are rotated by the agitator motor
1 for an appropriate time (preferably 1 to 5 hours), under application of
heat to a temperature ranging from room temperature to the boiling point
of the solvent (note that the temperature is not higher than 150°
C.) with the heater 3 if necessary. The agitation is stopped and the
content is allowed to stand. The resultant supernatant of the content in
the reaction vessel 4 is supplied via the pipe 14 to the purifier 13. The
lactic acid component in the content is separated and collected at the
purifier 13. The lactic acid component is separated and collected at the
purifier 13 as described above.

[0112]In a further different embodiment, a lactic acid fermentation
liquor, pH of which is adjusted to 4.8 or less by addition of an acid at
the pH adjusting vessel 5, is supplied via the liquid sending pump 6 to
the reaction vessel 4. A solvent is supplied from the solvent tank via
the liquid sending pump 7 to the reaction vessel 4. In the reaction
vessel 4, the lactic acid fermentation liquor and the solvent are
suspended by agitation of the agitator blades 2 that are rotated by the
agitator motor 1. The content of the reaction vessel 4 is heated by the
heater 3. When the content in the reaction vessel 4 is heated at least to
the azeotropic point of water and the solvent (e.g., 90° C. or
higher), the content starts to be evaporated. The vapor from evaporation
passes through the distillation column 8, and is cooled down and
condensed at the condenser 9, and flows down to the decanter 10. The
condenser 9 (or the condenser 9 and the decanter 10) is cooled down with
circulating chilled water or the like. In the decanter 10, the condensate
is separated into the solvent and water at the upper layer and at the
lower layer, respectively, due to the difference in specific gravities
because the solvent and water are not miscible. The solvent at the upper
layer flows back via the U-tube 11 to the distillation column 8. Because
of the pipe for the return path of U-shaped, the effect of water removal
is further increased. The solvent that has flowed back is refluxed
together with a solvent that is refluxed in the distillation column 8, to
be refluxed via the U-tube 12 to the reaction vessel 4. The reaction
vessel 4 is heating continuously until most of the water in the supplied
fermentation liquor is removed, and then the temperature for heating is
increased to the boiling point of the solvent (note that the temperature
is not higher than 150° C.), and the heating is further continued.
The heating and agitation are performed for an appropriate time
(preferably 5 to 24 hours), and then the agitation is stopped and the
content is allowed to stand while continuing the heating. The resultant
supernatant of the content in the reaction vessel 4 is supplied via the
pipe 14 to the purifier 13. The lactic acid component in the content is
separated and collected at the purifier 13. The lactic acid component is
separated and collected at the purifier 13 as described above.

[0113]In this embodiment, toluene, xylene, mesitylene, ethylbenzene, or
mineral spirit may be used as the solvent. Here, the separation and
collection of the lactic acid component at the purifier 13 will be
described. The content in the purifier 13 is cooled down by the cooling
device (not shown) to precipitate the solute of the content, and the
precipitated oligo (lactic acid) is collected. In this manner, the oligo
(lactic acid) produced by dehydration-condensation of the lactic acid is
separated and collected from the lactic acid fermentation liquor.
Furthermore, the supernatant of the content in the purifier 13 is
introduced via the pipe 15 into the solvent supply line, and is sent back
to the reaction vessel 4.

[0114]In a still further different embodiment, a lactic acid fermentation
liquor, the pH of which is adjusted to 4.8 or less by addition of an acid
at the pH adjusting vessel 5, is supplied via the liquid sending pump 6
to the reaction vessel 4. Then, the reaction vessel 4 is heated by the
heater 3 for an appropriate time (preferably 5 to 24 hours) to a
temperature ranging from 100 to 150° C., while the pressure in the
reaction vessel 4, the distillation column 8, and pipes connecting these
constituent elements is reduced, for example, to 10 to 100 torr (i.e.,
approximately 1330 Pa to approximately 13300 Pa), by the vacuum pump (not
shown) connected to the condenser 9. The content in the reaction vessel 4
starts to be evaporated. The vapor from evaporation passes through the
distillation column 8, and is cooled down and condensed at the condenser
9. The water from condensation is discharged from the pipe. The condenser
9 is cooled down with circulating chilled water or the like. Thus, the
lactic acid fermentation liquor in the reaction vessel 4 is subjected to
dehydration-condensation. Subsequently, the solvent is supplied from the
solvent tank via the liquid sending pump 7 to the reaction vessel 4. In
the reaction vessel 4, the lactic acid fermentation liquor subjected to
dehydration-condensation and the solvent are agitated by the agitator
blades 2 that are rotated by the agitator motor 1 for an appropriate time
(preferably 1 to 5 hours), under application of heat to a temperature
ranging from 60° C. to the boiling point of the solvent (note that
the temperature is not higher than 150° C.) with the heater 3. The
agitation is stopped and the content is allowed to stand while continuing
the heating. The resultant supernatant of the content in the reaction
vessel 4 is supplied via the pipe 14 to the purifier 13. The lactic acid
component in the content is separated and collected at the purifier 13.
The lactic acid component is separated and collected at the purifier 13
as described above.

[0115]In this embodiment, toluene, xylene, mesitylene, ethylbenzene, or
mineral spirit may be used as the solvent. Here, the separation of the
lactic acid component at the purifier 13 will be described. The content
in the purifier 13 is cooled down by the cooling device (not shown) to
precipitate the solute of the content, and the precipitated oligo (lactic
acid) is collected. In this manner, the oligo (lactic acid) produced by
dehydration-condensation of the lactic acid is separated and collected
from the lactic acid fermentation liquor. Furthermore, the supernatant of
the content liquid in the purifier 13 is introduced via the pipe 15 into
the solvent supply line, and is sent back to the reaction vessel 4.

[0116]The aforementioned apparatus can be used also in a case where for
the production of the oligo (lactic acid), the fermentation liquor is
heating under reduced pressure without using the solvent, and is washed
with water. A lactic acid fermentation liquor, pH of which is adjusted to
4.8 or less by addition of an acid at the pH adjusting vessel 5, is
supplied via the liquid sending pump 6 to the reaction vessel 4. Then,
the reaction vessel 4 is heated by the heater 3 for an appropriate time
(preferably 5 to 24 hours) to a temperature ranging from 100 to
150° C., while the pressure in the reaction vessel 4, the
distillation column 8, and pipes connecting these constituent elements is
reduced, for example, to 20 to 100 torr (i.e., approximately 2700 Pa to
approximately 13300 Pa), by the vacuum pump (not shown) connected to the
condenser 9. The content in the reaction vessel 4 starts to be
evaporated. The vapor from evaporation passes through the distillation
column 8, and is cooled down and condensed at the condenser 9. The water
from condensation is discharged from the pipe. The condenser 9 is cooled
down with circulating chilled water or the like. Thus, the lactic acid
fermentation liquor in the reaction vessel 4 is subjected to
dehydration-condensation. Subsequently, water is supplied from the
solvent tank via the liquid sending pump 7 to the reaction vessel 4. In
the reaction vessel 4, the lactic acid fermentation liquor subjected to
dehydration-condensation and the supplied water are agitated by the
agitator blades 2 that are rotated by the agitator motor 1 for an
appropriate time (preferably 0.5 to 5 hours), under application of heat
to a temperature up to the boiling point of water with the heater 3 if
necessary. Subsequently, the agitation is stopped and the content is
allowed to stand while continuing heating if heating is performed. A
supernatant aqueous solution with a lower specific gravity is discharged
via a pipe (that also may be the pipe 14). With this procedure, the
produced oligo (lactic acid) can be separated and collected in the
reaction vessel 4. The produced oligo (lactic acid) also may be further
polymerized by heating under reduced pressure in the reaction vessel 4.
After washing with water in the reaction vessel 4 to separate and collect
the oligo (lactic acid), this oligo (lactic acid) may be dissolved again
using the lactic acid component extracting solvent for separation and
collection in the purifier 13.

[0117]In this manner, a lactic acid component can be easily separated only
by using the solvent, and agitating the lactic acid fermentation liquor,
and if necessary, adjusting the temperature and/or reducing the pressure,
after adjusting the pH of the lactic acid fermentation liquor. Since only
the solvent supplied from the solvent tank is used, a lactic acid
component can be extracted with few impurities and at low cost.
Furthermore, the solvent used for extraction can be circulated and used
continuously, and thus a low-cost and safe apparatus without consumption
or leakage of the solvent can be obtained.

[0118]Hereinafter, the present invention will be specifically described
using examples, but the technical scope of the present invention is not
limited to these examples.

EXAMPLES

Example 1

[0119]In a lactic acid fermentation liquid medium that contained 3.5 wt %
of standard medium M17 (manufactured by Difco Laboratories) for
streptococcus, supplemented with 14 wt % of glucose, lactic acid bacteria
(streptococcus bacteria) were subjected to lactic acid fermentation in
suspension culture while the pH of the medium was adjusted with ammonia
to near 6, to obtain 20 g of lactic acid fermentation liquor (pH 6) in
which the concentration of ammonium lactate was 10 wt %. The cells of
bacteria were removed in advance from the lactic acid fermentation liquor
by centrifugal separation. The pH of the lactic acid fermentation liquor
was adjusted to 4.8 by addition of sulfuric acid. Subsequently, 50 ml of
xylene was added thereto, and the mixture was heated at 130° C.
with agitation in a reflux state. One hour later, the agitation was
stopped and the mixture was allowed to stand while continuing heating at
130° C., to separate it into two layers. When the upper layer was
collected and cooled down to room temperature, precipitation was
observed. The precipitation was due to lactic acid, and the yield of the
extraction was 10% (see Table 1 below).

Example 2

[0120]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 2.5 by addition of sulfuric acid. Subsequently, 50 ml of
xylene was added thereto, and the mixture was heated at 130° C.
with agitation in a reflux state. One hour later, the agitation was
stopped and the mixture was allowed to stand while continuing heating at
130° C., to separate it into two layers. When the upper layer was
collected and cooled down to room temperature, precipitation was
observed. The precipitation was due to lactic acid, and the yield of the
extraction was 20% (see Table 1 below).

Comparative Example 1

[0121]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. Here, the pH of the lactic acid fermentation
liquor was not adjusted. Then, 50 ml of xylene was added to the lactic
acid fermentation liquor, and the mixture was heated to 130° C.
with agitation. One hour later, the agitation was stopped and the mixture
was allowed to stand while continuing heating at 130° C. in a
reflux state, to separate it into two layers. When the upper layer was
collected and cooled down to room temperature, a small amount of
precipitation was observed. The precipitation was due to ammonium
lactate, and the yield of the extraction was as slight as 0.6% (see Table
1 below).

[0122]Table 1 below collectively shows the results of the extraction by
heating the lactic acid fermentation liquor with xylene.

[0123]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 4.8 by addition of sulfuric acid. Subsequently, 50 ml of
xylene was added thereto, and the mixture was heated to 100° C.
with agitation. A vapor was condensed, water from which was removed, and
then refluxed, and about 17 g of water was thus removed over
approximately 2 hours. Subsequently, the mixture was heated to
130° C. One hour later, the agitation was stopped and the mixture
was allowed to stand, to separate it into two layers. When the upper
layer was collected and cooled down to room temperature, precipitation
was observed. The precipitation was due to lactic acid, and the yield of
the extraction was 20% (see Table 2 below).

Example 4

[0124]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 2.5 by addition of sulfuric acid. Subsequently, 50 ml of
xylene was added thereto, and the mixture was heated to 100° C.
with agitation. A vapor was condensed, water from which was removed, and
then refluxed, and about 17 g of water was thus removed over
approximately 2 hours. Subsequently, the mixture was heated to
130° C. One hour later, the agitation was stopped and the mixture
was allowed to stand, to separate it into two layers. When the upper
layer was collected and cooled down to room temperature, precipitation
was observed. The precipitation was due to lactic acid, and the yield of
the extraction was 35.5% (see Table 2 below).

Comparative Example 2

[0125]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. Here, the pH of the lactic acid fermentation
liquor was not adjusted. Then, 50 ml of xylene was added thereto, and the
mixture was heated to 100° C. with agitation. A vapor was
condensed, water from which was removed, and then refluxed, and about 17
g of water was thus removed over approximately 2 hours. Subsequently, the
mixture was heated to 130° C. One hour later, the agitation was
stopped and the mixture was allowed to stand, to separate it into two
layers. When the upper layer was collected and cooled down to room
temperature, precipitation was observed. The precipitation was due to
lactic acid, and the yield of the extraction was 3.8% (see Table 2
below).

[0126]Table 2 below collectively shows the results of dehydration of the
lactic acid fermentation liquor by azeotropy with xylene.

[0127]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 4.8 by addition of sulfuric acid. Subsequently, 50 ml of
xylene was added to thereto, and the mixture was heated to 100° C.
with agitation. A vapor was condensed, water from which was removed, and
then refluxed, and about 17 g of water was thus removed over
approximately 2 hours. Subsequently, the mixture was heated to
139° C. Twenty hours later, the agitation was stopped and the
mixture was allowed to stand, to separate it into two layers. When the
upper layer was collected and cooled down to room temperature,
precipitation was observed. The precipitation was due to oligo (lactic
acid), and the yield of the extraction was 46.7%. A determination of the
molecular weight by gel permeation chromatography showed that the
weight-average molecular weight was 350 (see Table 3 below).

Example 6

[0128]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 2.5 by addition of sulfuric acid. Subsequently, 50 ml of
xylene was added thereto, and the mixture was heated to 100° C.
with agitation. A vapor was condensed, water from which was removed, and
then refluxed, and about 17 g of water was thus removed over
approximately 2 hours. Subsequently, the mixture was heated to
139° C. Twenty hours later, the agitation was stopped and the
mixture was allowed to stand, to separate it into two layers. When the
upper layer was collected and cooled down to room temperature,
precipitation was observed. The precipitation was due to oligo (lactic
acid), and the yield of the extraction was 63.6%. A determination of the
molecular weight by gel permeation chromatography showed that the
weight-average molecular weight was 698 (see Table 3 below).

Comparative Example 3

[0129]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. Here, the pH of the lactic acid fermentation
liquor was not adjusted. Then, 50 ml of xylene was added to the lactic
acid fermentation liquor, and the mixture was heated to 100° C.
with agitation. A vapor was condensed, water from which was removed, and
then refluxed, and about 17 g of water was thus removed over
approximately 2 hours. Subsequently, the mixture was heated to
139° C. Twenty hours later, the agitation was stopped and the
mixture was allowed to stand, to separate it into two layers. When the
upper layer was collected and cooled down to room temperature,
precipitation was observed. The precipitation was due to oligo (lactic
acid), and the yield of the extraction was 5%. A determination of the
molecular weight by gel permeation chromatography showed that the
weight-average molecular weight was 137 (see Table 3 below).

[0130]Table 3 below collectively shows the results of
dehydration-condensation of the lactic acid fermentation liquor by
azeotropy with xylene.

[0131]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 4.8 by addition of sulfuric acid. Subsequently, the lactic
acid fermentation liquor was heated to 150° C., and kept under
atmospheric pressure for 2 hours, under a reduced pressure of 100 torr
(approximately 13300 Pa) for 2 hours, and then under a reduced pressure
of 30 torr (approximately 4000 Pa) for 2 hours. Then, 50 ml of xylene was
added thereto, and the mixture was heated to 100° C. with
agitation. On hour later, the agitation was stopped and the mixture was
allowed to stand while continuing heating at 100° C., to separate
it into two layers. When the upper layer was collected and cooled down to
room temperature, precipitation was observed. The precipitation was due
to oligo (lactic acid), and the yield of the extraction was 35%. A
determination of the molecular weight by gel permeation chromatography
showed that the weight-average molecular weight was 250 (see Table 4
below).

Example 8

[0132]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 2.5 by addition of sulfuric acid. Subsequently, the lactic
acid fermentation liquor was heated to 150° C., and kept under
atmospheric pressure for 2 hours, under a reduced pressure of 100 torr
(approximately 13300 Pa) for 2 hours, and then under a reduced pressure
of 30 torr (approximately 4000 Pa) for 2 hours. Then, 50 ml of xylene was
added thereto, and the mixture was heated to 100° C. with
agitation. On hour later, the agitation was stopped and the mixture was
allowed to stand while continuing heating at 100° C., to separate
it into two layers. When the upper layer was collected and cooled down to
room temperature, precipitation was observed. The precipitation was due
to oligo (lactic acid), and the yield of the extraction was 60%. A
determination of the molecular weight by gel permeation chromatography
showed that the weight-average molecular weight was 637 (see Table 4
below).

Comparative Example 4

[0133]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. Here, the pH of the lactic acid fermentation
liquor was not adjusted. Then, the lactic acid fermentation liquor was
heated to 150° C., and kept under atmospheric pressure for 2
hours, under a reduced pressure of 100 torr (approximately 13300 Pa) for
2 hours, and then under a reduced pressure of 30 torr (approximately 4000
Pa) for 2 hours. Then, 50 ml of xylene was added thereto, and the mixture
was heated to 100° C. with agitation. On hour later, the agitation
was stopped and the mixture was allowed to stand while continuing heating
at 100° C., to separate it into two layers. When the upper layer
was collected and cooled down to room temperature, a small amount of
precipitation was observed. The precipitation was due to oligo (lactic
acid), and the yield of the extraction was 6%. A determination of the
molecular weight by gel permeation chromatography showed that the
weight-average molecular weight was 126. When the fermentation liquor was
near neutral, the molecular weight was not significantly increased even
with polymerization by heating under reduced pressure. Thus, the
solubility was not significantly changed either, and the yield was low
(see Table 4 below).

Example 9

[0134]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 2.5 by addition of sulfuric acid. Subsequently, the lactic
acid fermentation liquor was heated to 150° C., and kept under
atmospheric pressure for 2 hours, under a reduced pressure of 100 torr
(approximately 13300 Pa) for 2 hours, and then under a reduced pressure
of 30 torr (approximately 4000 Pa) for 2 hours. Then, 50 ml of water was
added thereto, and the mixture was heated at 100° C. for 1 hour
with agitation. On hour later, the agitation was stopped and the mixture
was allowed to stand while continuing heating at 100° C., to
separate it into two layers of a supernatant layer and a sediment layer.
When the sediment layer was collected and cooled down to room
temperature, precipitation was observed. The precipitation was due to
oligo (lactic acid), and the yield was 80%. A determination of the
molecular weight by gel permeation chromatography showed that the
weight-average molecular weight was 637 (see Table 4 below).

[0136]An apparatus, the configuration of which is shown in FIG. 1, was
used. In a lactic acid fermentation liquid medium that contained 3.5 wt %
of standard medium M17 (manufactured by Difco Laboratories) for
streptococcus supplemented with 20 wt % of glucose, lactic acid bacteria
(lactobacillus bacteria) were subjected to lactic acid fermentation in
suspension culture while the pH of the medium was adjusted with ammonia
to near 6, and thus a lactic acid fermentation liquor (pH 6) was
prepared, as an starting material, in which the concentration of ammonium
lactate was 14 wt %. The cells of bacteria were removed in advance from
the prepared lactic acid fermentation liquor by separation with a filter
membrane.

[0137]The lactic acid fermentation liquor was sent to the pH adjusting
vessel 5, where the pH of the lactic acid fermentation liquor was
adjusted to 2.5 by addition of sulfuric acid, and subsequently was
supplied via the liquid sending pump 6 to the reaction vessel 4.
Furthermore, xylene was supplied from the solvent tank via the liquid
sending pump 7 to the reaction vessel 4. The lactic acid fermentation
liquor, the pH of which had been adjusted to 2.5, and xylene were heated
at 100° C. for 2 hours with agitation. Then, the temperature was
increased to 120° C. A vapor obtained from evaporation was
condensed, water from which was removed, and then refluxed, and about 17
g of water was thus removed over approximately 5 hours (the total time
for heating at 100° C. and heating at 120° C.), at the
decanter 10. Subsequently, the mixture was heated to 139° C.
Twenty hours later, the agitation was stopped and the mixture was allowed
to stand, to separate it into two layers. When the upper layer was taken
from the pipe 14 and cooled down to room temperature at the purifier 13,
precipitation was observed. The precipitation was due to oligo (lactic
acid), and the yield of the extraction was 63.6%. A determination of the
molecular weight by gel permeation chromatography showed that the
weight-average molecular weight was 1500. The degree of crystallization
of the oligomer was as high as approximately 70%.

Example 11

[0138]As in Example 1 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 1. The pH of the lactic acid fermentation liquor was
adjusted to 2.0 by addition of sulfuric acid. Then, 200 ml of ethanol was
added thereto, and the mixture was agitated at room temperature. Thirty
minutes later, the agitation was stopped and the mixture was allowed to
stand. Then, it was observed that the mixture was separated into
precipitation at the lower layer and supernatant at the upper layer. The
upper layer was taken, and ethanol was removed therefrom by evaporation,
and thus, a viscous liquid was collected. The main component of the
collected liquid was lactic acid, and the yield of the extraction was
95%.

[0139]Here, the precipitation was due to the medium components used for
lactic acid fermentation and the salts used for neutralization or
acidification of the lactic acid fermentation liquor A calculation based
on the dry weight of the precipitation showed that 71.2 wt % of the
components other than the collected lactic acid were separated and
removed.

Example 12

[0140]In a lactic acid fermentation liquid medium that contained 1.3 wt %
of synthetic medium for lactic acid supplemented with 14 wt % of glucose,
lactic acid bacteria (lactococcus bacteria) were subjected to lactic acid
fermentation in suspension culture while the pH of the medium was
adjusted with ammonia to near 6, and thus 20 g of lactic acid
fermentation liquor (pH 6) was obtained in which the concentration of
ammonium lactate was 10 wt %. The synthetic medium contained ammonium
sulfate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate,
sodium chloride, magnesium sulfate, calcium chloride, sodium carbonate,
L-cysteine hydrochloride, and vitamins. The cells of bacteria were
removed in advance from the lactic acid fermentation liquor by
centrifugal separation. The pH of the lactic acid fermentation liquor was
adjusted to 2.0 by addition of sulfuric acid. Then, 200 ml of ethanol was
added thereto, and the mixture was agitated at room temperature. Thirty
minutes later, the agitation was stopped and the mixture was allowed to
stand. Then, it was observed that the mixture was separated into
precipitation at the lower layer and supernatant at the upper layer. The
upper layer was taken, and ethanol was removed therefrom by evaporation,
and thus, a viscous liquid was collected. The main component of the
collected liquid was lactic acid, and the yield of the extraction was
97%.

[0141]Here, the precipitation was due to the medium components used for
lactic acid fermentation and the salts used for neutralization or
acidification of the lactic acid fermentation liquor A calculation based
on the dry weight of the precipitation showed that 76.5 wt % of the
components other than the collected lactic acid were separated and
removed.

Example 13

[0142]As in Example 12 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 12. The pH of the lactic acid fermentation liquor
was adjusted to 2.0 by addition of sulfuric acid. Subsequently, 200 ml of
isopropyl alcohol was added thereto, and the mixture was agitated at room
temperature. Thirty minutes later, the agitation was stopped and the
mixture was allowed to stand. Then, it was observed that the mixture was
separated into precipitation at the lower layer and supernatant at the
upper layer. The upper layer was taken, and isopropyl alcohol was removed
therefrom by evaporation, and thus, a viscous liquid was collected. The
main component of the collected liquid was lactic acid, and the yield of
the extraction was 98%.

[0143]Here, the precipitation was the medium components used for lactic
acid fermentation and the salts used for neutralization or acidification
of the lactic acid fermentation liquor. A calculation based on the dry
weight of the precipitation showed that 82 wt % of the components other
than the collected lactic acid were separated and removed.

Example 14

[0144]As in Example 12 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 12. The pH of the lactic acid fermentation liquor
was adjusted to 2.0 by addition of sulfuric acid. Subsequently, 100 ml of
ethanol was added thereto, and the mixture was heated to 78° C.
with agitation. Water was evaporated and removed together with ethanol to
substantial dryness in approximately 2 hours. In the container, a viscous
liquid and a slightly yellow-tinged white precipitate remained. Further,
100 ml of ethanol was added into the container, and the mixture was
agitated at room temperature. Thirty minutes later, the agitation was
stopped and the mixture was allowed to stand. Then, it was observed that
the mixture was separated into precipitation at the lower layer and
supernatant at the upper layer. The upper layer was taken, and ethanol
was removed therefrom by evaporation, and thus, a viscous liquid was
collected. The main component of the collected liquid was lactic acid,
and the yield of the extraction was 95%.

[0145]Here, the precipitation was due to the medium components used for
lactic acid fermentation and the salts used for neutralization or
acidification of the lactic acid fermentation liquor. A calculation based
on the dry weight of the precipitation showed that 90 wt % of the
components other than the collected lactic acid were separated and
removed.

Example 15

[0146]As in Example 12 above, 20 g of lactic acid fermentation liquor (pH
6) was obtained in which the concentration of ammonium lactate was 10 wt
%. The cells of bacteria were removed from the lactic acid fermentation
liquor as in Example 12. The pH of the lactic acid fermentation liquor
was adjusted to 2.0 by addition of sulfuric acid. Subsequently, the
lactic acid fermentation liquor was heated to 50° C., and kept
under a reduced pressure of 10 torr (approximately 1330 Pa) for 2 hours,
and then under a reduced pressure of 5 torr (approximately 670 Pa) for 2
hours to substantial dryness. Then, 100 ml of ethanol was added thereto,
and the mixture was agitated. Thirty minutes later, the agitation was
stopped and the mixture was allowed to stand, to separate it into
supernatant and precipitation. The upper layer was taken, and ethanol was
removed therefrom by evaporation, and thus, a viscous liquid was
collected. The main component of the collected liquid was lactic acid,
and the yield of the extraction was 90%.

[0147]Here, the precipitation was due to the medium components used for
lactic acid fermentation and the salts used for neutralization or
acidification of the lactic acid fermentation liquor. A calculation based
on the dry weight of the precipitation showed that 94 wt % of the
components other than the collected lactic acid were separated and
removed.

Example 16

[0148]An apparatus, the configuration of which is shown in FIG. 1, was
used. In a lactic acid fermentation liquid medium that contained 3.5 wt %
of standard medium M17 (manufactured by Difco Laboratories) for
streptococcus supplemented with 15 wt % of glucose, lactic acid bacteria
(lactobacillus bacteria) were subjected to lactic acid fermentation in
suspension culture while the pH of the medium was adjusted with ammonia
to near 6, and thus a lactic acid fermentation liquor (pH 6) was prepared
as a starting material in which the concentration of ammonium lactate was
10 wt %. The cells of bacteria were removed in advance from the prepared
lactic acid fermentation liquor by separation with a filter membrane.

[0149]The lactic acid fermentation liquor was sent to the pH adjusting
vessel 5, where the pH of the lactic acid fermentation liquor was
adjusted to 2.0 by addition of sulfuric acid, and subsequently was
supplied via the liquid sending pump 6 to the reaction vessel 4. Then,
the lactic acid fermentation liquor, the pH of which had been adjusted to
2.0, was heated at 60° C. for 2 hours, while the pressure in the
reaction vessel 4, the distillation column 8, and pipes connecting these
constituent elements was reduced to 5 torr (approximately 670 Pa) by the
vacuum pump (not shown) connected to the condenser 9. Thus, the lactic
acid fermentation liquor in the reaction vessel 4 was dehydrated.
Subsequently, ethanol was supplied from the solvent tank via the liquid
sending pump 7 to the reaction vessel 4, and the mixture in the reaction
vessel 4 was agitated. Thirty minutes later, the agitation was stopped
and the mixture was allowed to stand, to separate it into two layers of
supernatant and precipitation. The supernatant was taken from the pipe 14
and guided to the purifier 13, and the solvent was removed by evaporation
from the supernatant by heating while the pressure was reduced by a
vacuum pump (not shown) attached to the purifier 13, and thus, a viscous
liquid was collected. The main component of the collected liquid was
lactic acid, and the yield of the extraction was 98%. Here, the solvent
removed by evaporation was ethanol, and may be cooled down and liquefied
through the pipe 15, and used again as the extracting solvent.

INDUSTRIAL APPLICABILITY

[0150]According to the present invention, a lactic acid component (e.g.,
lactic acid or oligo (lactic acid)) can be obtained from a lactic acid
fermentation liquor with a simple process. Accordingly, the present
invention may be a fundamental technique to synthesize, at low cost,
polymers such as polylactic acid and polyester polyol from the lactic
acid component as a starting material.